Messages in this thread | | | Date | Tue, 7 Apr 2015 13:58:38 -0400 | From | Dave Jones <> | Subject | Re: Hang on large copy_from_user with PREEMPT_NONE |
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On Tue, Apr 07, 2015 at 10:33:49AM -0700, Linus Torvalds wrote: > On Tue, Apr 7, 2015 at 10:00 AM, Sasha Levin <sasha.levin@oracle.com> wrote: > > > > It locks up quickly without KASan as well. > > I suspect it's some virtualization artifact, where the writes cause > COW faults (or just memory allocations) in the L0 domain. > > Whatever. It's probably not worth fighting. Either we just decide that > "copy_from_user()" shouldn't bother to zero huge areas (limit the > zeroing to some arbitrary size), or we just special-case the module > loading. > > +#define COPY_CHUNK_SIZE (16*PAGE_SIZE)
This needs to be bigger, just to accomodate things like xfs, which on my system is over 1mb. I think some out-of-tree modules (not that I care deeply) are even bigger.
Special casing might be an easier call.
Dave
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